title: Studies on the binding site of the galactose-specific agglutinin PA-IL from Pseudomonas aeruginosa.
abstract: The binding properties of Pseudomonas aeruginosa agglutinin-I (PA-IL) with glycoproteins (gps) and polysaccharides were studied by both the biotin/avidin-mediated microtiter plate lectin-binding assay and the inhibition of agglutinin-glycan interaction with sugar ligands. Among 36 glycans tested for binding, PA-IL reacted best with two glycoproteins containing Galalpha1-->4Gal determinants and a human blood group ABO precursor equivalent gp, but this lectin reacted weakly or not at all with A and H active gps or sialylated gps. Among the mammalian disaccharides tested by the inhibition assay, the human blood group Pkactive Galalpha1-->4Gal, was the best. It was 7.4-fold less active than melibiose (Galalpha1-->6Glc). PA-IL has a preference for the alpha-anomer in decreasing order as follows: Galalpha1-->6 >Galalpha1-->4 >Galalpha1-->3. Of the monosaccharides studied, the phenylbeta derivatives of Gal were much better inhibitors than the methylbeta derivative, while only an insignificant difference was found between the Galalpha anomer of methyl- and p -NO2-phenyl derivatives. From these results, it can be concluded that the combining size of the agglutinin is as large as a disaccharide of the alpha-anomer of Gal at nonreducing end and most complementary to Galalpha1-->6Glc. As for the combining site of PA-IL toward the beta-anomer, the size is assumed to be less than that of Gal; carbon-6 in the pyranose form is essential, and hydrophobic interaction is important for binding.
authors.affiliation: Glyco-immunochemistry Research Laboratory, Institute of Molecular and Cellular Biology and Graduate Institute of Clinical Medicine, Chang-Gung Medical College, Kwei-san, Tao-yuan, 333, Taiwan.
authors.forename: C P
authors.initials: CP
authors.lastname: Chen
authors.forename: S C
authors.initials: SC
authors.lastname: Song
authors.forename: N
authors.initials: N
authors.lastname: Gilboa-Garber
authors.forename: K S
authors.initials: KS
authors.lastname: Chang
authors.forename: A M
authors.initials: AM
authors.lastname: Wu
mesh_terms: D000017:ABO Blood-Group System / Q000378:metabolism; D018829:Adhesins, Bacterial / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D037102:Lectins / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000378:metabolism*
chemical_list: D000017:ABO Blood-Group System; D018829:Adhesins, Bacterial; D006023:Glycoproteins; D037102:Lectins; D011134:Polysaccharides; C038692:adhesin, Pseudomonas